


Promises to Keep

by Darkglade



Category: Toaru Kagaku no Railgun | A Certain Scientific Railgun, Toaru Majutsu no Index | A Certain Magical Index
Genre: Gen
Language: English
Status: In-Progress
Published: 2020-10-27
Updated: 2020-10-27
Packaged: 2021-03-08 18:29:12
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,652
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27221254
Author URL: https://archiveofourown.org/users/Darkglade/pseuds/Darkglade
Summary: The three of them promised to always be together. So, the first thing Misaki does is pull Mitori and Dolly into her school.
Comments: 2
Kudos: 26





	Promises to Keep

“How would you two like to go to school?”

Mitori choked on her drink. Several ounces of extravagant tea went down the wrong windpipe as she contemplated the ludicrous idea of someone like her, a former terrorist and agent of Academy City’s darkness doing something as mundane as going to _school_.

Dolly, on the other hand, was jumping up and down like Christmas had come early. “Can I really, Misaki-chan?!”

Misaki smiled. “Of course! With my ability, inventing a background for you two is child’s play.”

“When you say ‘school,’ you’re talking about Tokiwadai, aren’t you?” Mitori asked, wiping her mouth with her sleeve.

“Would I suggest any other? I desire only the best for my two dear friends, after all.”

“It sure is prestigious and all that, but doesn’t it have quite a lot of annoying rules and regulations too?”

“Well, yes it does. I’m not too bothered by them though,” Misaki said with a wink.

Mitori sighed. Truly, Mental Out was the premier weapon of convenience. But that wasn’t her only concern as she recalled the girl in a Tokiwadai uniform who had chased her down, cornered her in the sewer, and beat her up.

Not exactly her finest moment.

“I got into a scuffle with a Tokiwadai girl, remember? It might be awkward if I see her again.”

Misaki waved a hand dismissively. “Ah, that Judgement girl, right? It’s all water under the bridge. Besides, I did a lot of covering up after the Daihaseisai festival, so I’m sure she doesn’t remember anything about you.” She leaned in closer, trapping her with that starry-eyed gaze. “What’s the matter? Don’t want to go back to school?”

Mitori paused. It wasn’t that she _disliked_ school, but rather, the prospect of mingling with simpleminded teenage girls after everything that had happened to her seemed rather dull.

Working in the dark side of Academy City, for all its faults, was never a dull moment. Nothing like living on life’s edge to keep her sharp – letting her guard down for even a second was liable to end up with her dead in a ditch somewhere.

Heck, even working as Misaki’s informant wasn’t half-bad; she got to snoop around where she didn’t belong and dig up dirty secrets that other people most certainly wanted to keep to themselves. Compared to all that, going back to sitting in a classroom and trawling her way through homework again sounded unappealing to say the least.

“Mi-chan . . .”

Mitori turned to look at Dolly.

It was a fatal mistake.

_Grrk!_

Those wide eyes, those trembling lips. They were a vicious weapon that punched straight through Mitori’s heart.

“Don’t you want to go to school with me, Mi-chan?”

_This girl is going to be the death of me one of these days._

“Yes! Definitely! Can’t wait!” Mitori said with forced cheer.

Dolly gasped in delight and clasped their hands together. “Yay, Mi-chan is coming along! I can’t wait to go to class, meet new friends, do homework, get yelled at by the teacher, get detention –”

“Don’t _try_ to get detention!”

* * *

The Tokiwadai uniform felt itchy.

While Mitori stood there, fidgeting in her brand-new uniform, Dolly was taking the opportunity to drink in every last inch of the school’s interior, gaze darting around all over the place like she thought every nook and cranny might hold some sort of exciting marvel.

“Wow, it’s so big and pretty!” Dolly exclaimed.

“Eh, it’s alright I guess.”

After spending years attending Kirigaoka Girls' Academy, a school that was almost just as prestigious as Tokiwadai, the school’s splendor hardly grabbed her attention. This pretty façade was all just to cover up the ugly realities hiding in the city’s darkness anyway.

A group of giggling girls passed by, their gazes lingering on the two of them until Mitori’s glare sent them scurrying away.

Just when would their guide get here already? Bad enough that students transferring in the middle of the semester was rare and already made them noteworthy, but now they had to put up with a stuck-up rich girl showing them around and praising the school’s ostentatiousness.

“Ah, hello there! Are you our guide?” Dolly asked.

Mitori turned towards the newcomer and felt herself freeze. Tawny hair, twin pigtails, and red ribbons –

The newcomer bowed, unaware of her sudden distress.

“I am Shirai Kuroko, and yes, I will be the one to give you a tour of the school.”

Dolly beamed as she bowed back. “Nice to meet you! I’m Dolly.” She grabbed Mitori’s frozen form and pulled her over. “And this is my friend, Mi-chan!”

Mitori plastered a smile on her face, doing her best to pretend that she hadn’t been trying to violently murder the girl in front of her a few weeks ago.

“K – Kouzaku Mitori. It’s a pleasure.”

Luckily, the girl simply nodded and waved at them to follow along instead of trying to arrest her on the spot. Mitori knew that she would run into her again sooner or later, but she hadn’t expected it to be quite _this_ soon.

“Forgive me for prying, but it is unusual for our school to have transfer students in the middle of the semester,” Kuroko said as they walked together. “I presume that you two have some special circumstances?”

“Dolly has been in the hospital for a very long time,” Mitori explained, reciting their cover story. “She has only recently gotten better, and this is her first opportunity to go to school.”

It wasn’t even a lie. Well, mostly. A research institute was quite similar to a hospital, wasn’t it? They both poked at you with strange instruments and made you do weird tests for reasons they couldn’t be bothered to explain.

“I transferred here as well to help support her,” she finished.

Dolly hugged her from the side, pulling them closer together. “Mi-chan is the best! I love Mi-chan.”

Mitori flushed, embarrassed at the open display of affection in a public area. Kuroko was staring at the two of them with wide eyes, no doubt already labeling the two of them as a pair of lovey-dovey weirdos.

“To think such pure love could exist! If only Onee-sama could see that my love was this pure, maybe she’ll let me hug her like that too without shocking me. . .” the other girl murmured, her face growing more and more disturbing by the moment.

Mitori felt a sweat drop roll down her back. Maybe it was true what they said about how all higher-level espers were crazy.

* * *

Kuroko led them around all over the school, pointing out places of interest like the library, the clinic, the dorms, the cafeteria, the research labs . . . Mitori carefully noted down the locations of all these important areas since she was certain that Dolly was too busy gawking at the scenery to remember where everything was.

Finally, their guide showed them to an outdoor area with several tables scattered around, each holding an assortment of items such as sandbags, metal pipes, and paper cards.

“Please wait here,” Kuroko said. “An evaluator will be out shortly to conduct your ability tests.”

Mitori sighed in exasperation, tired from trekking all over the school. “Is this really necessary? Our records clearly show that I am level 4, and that Dolly is level 3.”

“Even so, the school still needs to verify the information for themselves. You two weren’t present for our most recent System Scan, so it can’t be helped.”

With that said, the girl turned and walked away, likely heading back to class.

“Woah, I wonder what all this is for.”

Mitori turned around to find Dolly poking around the tables. “Props to measure our abilities with, I suppose. They’ll probably ask you to magnetize some of these metal pipes or something similar.” She scratched her head as a thought occurred to her. “I can’t use any of these though, so I hope they won’t mind that I brought my own material.”

Her ability allowed her to freely control any liquids with a specific gravity of twenty or more. While powerful and versatile, it suffered from requiring one of these very specific liquids to be present for it to be of any use. Thus, Mitori had resigned herself to carrying around a jar of liquid metal in her bag wherever she went – it wouldn’t do to be caught unprepared, after all.

“Oh, are you going to show them those cute, swimming dolphins?”

“They’ll probably ask me to do something more complex, like turning it into a humanoid figure and having it do a bunch of acrobatic tricks.”

Dolly gasped and leaned forward. “You can make a doll now? Show me, show me!”

Mitori stepped back, trying to placate the uncontrollable bundle of excitement in front of her. “Alright, alright, sheesh.”

She took the jar of liquid metal out of her bag and popped off the top, laying it to the side. The calculations flowed through her mind like a gentle stream as she siphoned liquid from the jar and molded it into the desired shape. Before long, her life-sized puppet stood before her.

“Wow, it really looks just like you! You even gave it the same hair style!”

“It’s easier to control if it has the same shape as my body,” Mitori explained.

Dolly giggled, poking a finger into the puppet’s torso. “Ah, it feels cold! And kind of weird. Ah – !”

The puppet’s face had shifted downward towards where Dolly’s finger was stuck in its body. One-by-one, Mitori had the puppet shift through a variety of comically exaggerated faces.

“Ahahaha, you made its nose so big, Mi-chan! Ahahaha – ”

“I see you two are having fun.”

The two of them whipped around to find a woman walking towards them with a stern expression. “We forbid the unregulated use of esper abilities on school grounds, you know?”

“Ah, sorry, sorry, I got carried away,” Mitori said with a sheepish smile.

Dolly shook her head. “No, no, it’s my fault; I’m the one who asked Mi-chan to do this.”

The woman sighed, a ghost of a smile appearing on her face. “Since you two are new here, I’ll let it slide this time.” She walked over to the tables. “Anyway, let’s begin your evaluations.”

* * *

“Hold it there. Yes, just like that. Keep it steady, try to not let it move even an inch,” the evaluator instructed.

After hovering in the air for several more tenuous seconds, the metal crate dropped to the ground with a thud, a panting Dolly standing next to it.

Mitori clapped softly, a small smile on her face. “That was great, Dolly! At this rate you’ll level up in no time.”

Dolly beamed. “Hehe, I still have a long way to go before I’m as amazing as you, Mi-chan, but I’ll do my best!”

The evaluator nodded. “That should be sufficient.” She turned towards Mitori. “We can begin your evaluation now, Kouzaku-san. I’m afraid we do not have any liquids suitable for your ability in storage, so it is a good thing that you brought your own.”

“Yeah, I’m quite used to it.” The liquid metal sprang up next to her, reforming itself into her puppet once more. “What do you want me to do?”

“Hmm . . .” The woman tapped her chin. “Your ability is quite rare, so I’m afraid I’m uncertain as to how best to measure it. In fact, I’m surprised that you’re attending Tokiwadai instead of Kirigaoka Girls' Academy; I believe they specialize in raising students with rare abilities such as yourself.”

Funny the woman should mention Kirigaoka since that _was_ , in fact, the school she had attended before she fell into the dark side of Academy City.

“I have personal reasons for deciding to attend here instead,” Mitori said. “But that is beside the point. How about I just demonstrate what I can do? Maybe that’ll give you a few ideas.”

“Very well. Show me what you can do.”

There were several targets scattered about, remnants of when Dolly had been tested on her ability to fire her best railgun at them using small screws as ammunition. With a flick of her hand, the puppet’s arm elongated into a sharp spike that stretched out and pierced through the targets, zigging-zagging between them to punch through the center of each one.

“Impressive range and control. How far away can it go?”

“I’ve maintained control at ranges as long as fifty meters.”

The woman nodded, writing something down. “Why don’t we try some small, moving targets? I’ll throw a bunch of screws into the air, and you’ll need to grab them with your puppet.” She grabbed a fistful of screws and proceeded to do just that.

Viscous tendrils whipped out of the puppet, snatching the screws out of the air one-by-one as they reached the peak of their arc. After grabbing them all, she deposited them back onto the table.

“Very good, very good. Now, I have just one last test for you.”

“And what would that be?”

The woman spun around, hurtling something in her direction. Mitori reacted instinctively, sending her puppet to reach up and intercept the flying . . . purse?

“My, my, I see you’re as quick on the draw as always, Mitori-san.”

She sighed. “Was that really necessary, Misaki-chan?”

The woman laughed, her eyes glazed over with stars. “I’m just keeping you on your toes, that’s all. Wouldn’t want you to become lax at school.”

“Trust me, I know very well what a pit of vipers a school can be. Especially an all-girls school.”

Dolly’s gaze was snapping back-and-forth between the two of them, trying to follow their conversation. “Wah? Is that you, Misaki-chan?”

The starry-eyed woman smiled and waved at Dolly. “Hi-hi! Yes, it’s me! I just wanted to check up on you two and see how you were doing, but unfortunately I couldn’t come in person.”

Mitori rolled her eyes. “Don’t be fooled by her words, Dolly. I’m sure Misaki-chan was simply too lazy to walk over here in person so she decided to irresponsibly use her power instead.”

“How rude! A proper lady must not carelessly expose herself to the elements. Besides, I’ll have you know that I am, in fact, stuck in a tea party with some sycophants from my clique.”

“Why don’t you just mind-control them to leave you alone?”

“Because I’m not quite as frivolous with my ability as you seem to believe.”

“So instead of using your power on your clique members, you decided to use it on a teacher instead?” Mitori sighed as she shook her head. “You really did just wanted to avoid walking here yourself, didn’t you? Whatever you do, Dolly, don’t grow up to be a lazy bum like Misaki-chan here.”

“Haha . . . ahahahaha!”

Mitori turned to find Dolly lying on the ground, laughing uncontrollably.

“Mi-chan . . . Misaki-chan . . . you’re so funny! Ahahahaha – ”

In a moment of unity, Mitori felt herself and Misaki simultaneously sweat drop at the scene in front of them.

“Anyway, what’s in this?” Mitori asked, peeking into the purse clutched in her puppet’s hands.

“Ah, it’s just some money for living costs and a pair of cell phones so we can keep in touch,” the starry-eyed woman said.

Dolly leapt off the ground and dashed forward, eyes glittering. “Ooooh, a cell phone! For me?”

“Indeed. I already took the liberty of putting our numbers in, so now we can talk whenever we want!”

As Dolly stared at her newly acquired cell phone, holding it reverently like it was the holy grail itself, Mitori felt a smile spread across her face.

“Thanks, Misaki-chan. You didn’t have to go through the trouble – ”

“Nonsense, what are friends for? Ah, but I should let you finish up here, shouldn’t I? Ta-ta – ”

The woman blinked, her starry-eyed gaze vanishing in a split second. “Hmm? What was I . . . .” Her eyes focused on Mitori, recognition flashing back in. “Oh, Kouzaku-san. I think I’ve seen enough to know that you demonstrate an impressive mastery of your ability.” She nodded to herself. “I’ll be off to update your records. You two girls can go home now; classes are almost over anyway.”

As the woman walked off, Mitori let out a deep breath. Since she and Dolly were now students at Tokiwadai, Misaki had also arranged for them to stay in the school’s dorm in School Garden as well.

“Come on, Dolly, let’s go see what kind of super high-class room Misaki-chan got for us.”

As Mitori turned to leave, she felt a hostile glare being levered at her.

“You’ve got some nerve, showing your face here.”

A chestnut-haired girl approached, sparks dancing off her short bangs. Her eyes stared intently at Mitori, filled with a recognition that made the former dark-side agent very, very uncomfortable.

_Oh, right, Railgun attends this school too, doesn’t she?_

After taking the girl’s friend and mother hostage in a failed attempt to interrogate her about her clones and then leading her around by the nose while she was being forcibly powered up to level 6, she would say that the history between the two of them wasn’t exactly stellar.

_But how does she recognize me? I didn’t talk to her personally the first time, and I doubt she was cognizant enough to know who was talking to her during that stupor!_

“I’ll admit, I wasn’t sure it was you at first, but after seeing your ability in action . . . well, I doubt there’s anyone else who looks just like you _and_ has that kind of unique ability,” the girl said.

Mitori looked to the side and found her puppet slowly dissolving now that she wasn’t paying any attention to it.

_Fuck._

She raised her arms in the air, putting on her best disarming grin. “Now, now, I think we have a little misunderstanding here – ”

Railgun grabbed her collar and pulled her in close, sparks still flying off her in spades. “What’s your game here? Trying to get at my sisters again? I knew students transfering in during the middle of the semester was suspicious – ”

Someone’s arm intervened, pulling the angry and extremely hazardous level 5 off of Mitori. That same person stepped in between them, spreading out her hands in front of Mitori protectively.

“Don’t bully Mi-chan!” Dolly said with a fierce gaze.

Mitori stared at the chaos unfolding in front of her and wondered how Misaki could’ve missed something this big.

* * *

Mikoto stared at the girl standing between them. A girl with hair the same shade as hers and wearing an expression of stubborn defiance that struck a chord within her.

_Is she an accomplice? It would explain why they transferred in together._

“Get out of the way,” she growled.

The girl shook her head. “I don’t know what you want with Mi-chan, but I won’t let you hurt her!”

Mikoto considered zapping the girl and knocking her out. But there was something sincere about the girl’s actions, like she really was just trying to protect her friend.

She couldn’t hate people like that.

Putting on her friendliest smile, she switched tactics. “Hey now, I’m not going to hurt her. I just want to talk.”

The girl gave her a doubtful look. “Then you can talk just fine from there, can’t you?”

Mikoto sighed. “Fine, then.” She glared at the purple-haired girl, who had been trying to slip away in the meantime. “What are you doing here? Are you after my sisters again?”

The other girl paused, looking at her in the eye. “I’m just here to go to school. That’s all. Besides, why would I be after your sisters when one of them is right here?”

Mikoto frowned. “Huh?”

“What are you talking about, Mi-chan?”

The purple-haired girl smirked. “I suppose I should introduce you two. Dolly, meet your big sister, Misaka Mikoto.”

Dolly turned to her, eyes widening. Her mouth split into a huge grin and she rushed forward with her arms outstretched. “Onee-chan!”

“Gah!”

Mikoto stumbled backwards as Dolly threw herself into a hug. Was it true? Was this girl really yet another long-lost sister? Or was it merely a coincidence that they shared the same hair color, the same ability, the same earnest, heartfelt desire to protect those close to them –

This close, Mikoto could feel the other girl’s heartbeats, could feel the electrical signals coursing through her system. They were in sync – _far_ too closely in sync.

There was no doubt about it.

Grimacing, she tried to pry her newly discovered sister off, but it seemed that the girl hugged even more tightly than Kuroko. And not only were her electric shocks less effective against her sister since she was also an electromaster, but she would feel guilty if she pushed her ability far enough to hurt her.

After promising the other girl that she would play with her later as well as making several other dubious promises that she may or may not have been paying attention to the contents of, she finally managed to pry her off, only to find that the purple-haired girl had escaped in the meantime.

“Jeez, where did she go?” Mikoto mumbled.

Dolly, however, seemed unruffled by the sudden absence of her companion. “Ah, I made a new friend on my first day of school! I can’t wait to tell Misaki-chan!”

The gears in Misaka’s brain ground to a halt as she heard the name of a certain very troublesome Mental Out.

* * *

“My, my, if it isn’t Misaka-san. It’s quite rare for you to seek me out of your own volition.”

Mikoto grimaced as she sat down across from Misaki, trying to not let the other girl’s smirk get to her. “You’ve got some explaining to do, Shokuhou.”

“Whatever could you mean?”

“Don’t play dumb with me. You’re the one who pulled the strings to let those transfer students get in, aren’t you?”

“And so what if I did?”

“You of all people must know that one of them is a terrorist who was involved in a plot to destroy Academy City.”

Misaki’s gaze did not waver in the slightest. “She was involved in something like that at one point, yes.”

Mikoto stared at her incredulously. “So why the heck would you enroll someone like _that_ in Tokiwadai Middle School?!”

Her rival sighed, her smug expression softening into something resembling nostalgia. “Do you remember the girl who was with her?”

Mikoto paused. How could she forget? She didn’t think it was possible for there to be a girl who was clingier than Kuroko. “Yeah.”

“Then let me tell you the story of a girl named Dolly . . .”

Mikoto listened intently, learning of a lonely girl and the two friends she had made in a cold, merciless research institution. By the time the story was done, she was seething, outraged that the atrocities that happened because of her careless donation of her DNA map had ran even deeper than she had thought.

Taking a deep breath, she forced herself to calm down. What’s done was done, and it seemed that this sister was able to find happiness in the end, at least.

“So it was all for revenge, then? She wanted to destroy Academy City just to avenge one girl?” Mikoto asked.

“I figured you would sympathize with her circumstances, Misaka-san. After all, didn’t you go on a rampage against Academy City yourself once you learned of your sisters’ plight?” Misaki replied.

“At least I only targeted the facilities involved and didn’t drag innocents into it!”

“Not everyone can be as picky as you, Misaka-san. We are level 5’s who stand above everyone else in this city. We can act as we please, and more likely than not, the city will bend over to accommodate us.”

Misaki paused, sipping her tea. “She, on the other hand, is a measly level 4. There are plenty of others like her, so the city has no qualms with stamping her out if she tries to rebel. She can struggle all she wants, but nothing will change the fact that she cannot stand against the city by herself. So, she needed help; help that only the devil could provide.” Her lips curled up in distaste. “That devilish old man offered his price, and what could she do but accept?”

Mikoto frowned. “She could’ve just said no.”

“And give up on her revenge entirely? Could you have made that choice yourself, Misaka-san? You were all too willing to throw your own life away, but if it were the lives of others instead, could you have made the same choice? If you had to choose between a revenge that hurt innocents or no revenge at all, could you say with utter certainty that you would give up?”

She wanted to say yes. She wanted to say that she would give up, that she would do the moral, just thing, that she really did have a line that she wasn’t willing to cross.

But she couldn’t do it.

In the depths of her despair, even giving up her own life had seemed like an acceptable choice if it would stop the experiment. What was to say that a little nudge couldn’t have set her on a darker path, that if things went a little differently, she really might have stained her hands with blood for the sake of her sisters?

If the devil had offered a deal to her during those horrid, bleak days, she really might have accepted.

Mikoto looked up to find Misaki looking at her with what she dared to say was a comforting expression.

“It seems you’ve come to a conclusion. But let’s move on from this dreary topic, shall we? The weather is far too nice to dwell on such heavy matters,” Misaki said.

Mikoto chuckled weakly. “I suppose so.” She paused to take a sip of tea as well. “So if she really is just here to go to school alongside Dolly like she claimed, why didn’t you just tell me about it? We could’ve avoided this whole misunderstanding.”

“Ah, but where’s the fun in that? I thought this way was much more entertaining.”

Mikoto felt her eyebrows twitch in irritation. “Is that so?”

“Indeed. A bit of harmless fun every now and then is healthy for the body, wouldn’t you agree?”

“I doubt your _friend_ would think the same if I ended up hurting her because of this misunderstanding!”

Misaki grinned. “Ah, but I know you, Misaka-san. You’re a lot nicer than you look.”

“Hey, what’s that supposed to mean!”

The other girl ignored her protests. “After all, why do you think I let myself be alone with you during the Daihaseisai Festival incident despite the fact that I had recently wiped your friends’ memories and you had every reason to have a grudge against me? With your immunity to my ability, I might as well be a defenseless level 0 before you.”

Mikoto paused. Come to think of it, she _had_ thought that Misaki coming out alone to meet her that time was rather strange and unlike the normally cautious girl.

“Despite your hotheaded attitude and propensity for violence, you’re a good person, Misaka-san. Someone who shows mercy to even her enemies.” Misaki smiled. “I trusted that you wouldn’t attack me back then, and I trusted that you wouldn’t attack my friend now. That’s all.”

“You’re putting an awful lot of trust into someone whose mind you can’t even read.”

“Ah, but that’s part of the fun! It’s more entertaining precisely because I cannot know the outcome with one-hundred percent certainty.”

Mikoto shook her head. “To think that the Number Five esper gets a thrill out of risk taking . . . I shudder to think of the day you can legally gamble.”

Misaki puffed out her cheeks. “Playing slots wouldn’t be any fun, and even games like poker would be trivial with my ability. Unless you were also at the table.” A pause. “Actually, it would still be trivial even if you were at the table. You’re a pretty terrible liar.”

“Hey!”

**Author's Note:**

> AN:  
> Hello and welcome to a story of dubious quality about a popular character and two other super obscure characters. I couldn't find any fics about this cute trio, so I decided to bite the bullet and write one myself.   
> As for where this story is going, well, that’s not locked in yet. Maybe I’ll write it like a Railgun arc (like the stories written by Cun and GreatSnapper, they’re both great authors you should go check them out) or maybe I’ll write this like a series of interconnected one-shots. Guess we’ll find out once I’ve written the second chapter. :P


End file.
